High mechanical strength sorbent product, system, and method for controlling multiple pollutants from process gas

ABSTRACT

A sorbent product, including from about 1 wt % to about 99 wt %, based on the total weight of the sorbent product, of at least one base sorbent material; and from about 1 wt % to about 99 wt %, based on the total weight of the sorbent product, of at least one binder. The sorbent product may further include at least from about 0 wt % to about 99% wt %, based on the total weight of the sorbent product, of at least one additional additive. Methods for making same and methods and systems for controlling multiple pollutants are also included.

TECHNICAL FIELD OF THE INVENTION

This invention relates, in general, to controlling multiple pollutantsfrom process gas and, in particular, to a high mechanical strengthsorbent product, system, and method for controlling multiple pollutantsfrom process gas.

BACKGROUND OF THE INVENTION

Without limiting the scope of the present invention, its background willbe described in relation to a high mechanical strength sorbent product,system, and method for controlling multiple pollutants from process gas,as an example.

The United States continually strives for cleaner energy production todecrease the detrimental impacts to our environment. For coal-firedpower plants in particular this is a challenge that involvesimplementation of various pollution control devices. Over the years, asregulations continue to tighten and include more contaminants ofconcern, novel technologies that can remove multiple pollutantssimultaneously have become popularized.

Activated carbon is a well-known material commonly used for treatment ofa multitude of pollutants from gas and liquid streams. Activated carbonscontinue to find new treatment applications across many industries. Incoal-fired power application, activated carbons have most recently beenused to remove mercury from flue gas streams for protection of theenvironment. In other process gases, activated carbons have beendemonstrated to remove sulfur dioxide (SO₂) and volatile organiccompounds (VOCs). Typically these applications involve using a specificactivated carbon that has properties that are optimized for theparticular pollutant. Certain characteristics that are ideal for onecontaminant are not so for another. Therefore, the current state of artto control for various pollutants from process gas or flue gas iscomprised of different targeted pollution control technologies to removeeach pollutant individually.

For instance, using flue gas generated from coal-fired power production,nitrogen oxides (NOx), sulfur oxides (SO_(x)), and mercury are regulatedpollutants that require specific pollution control equipment to removethem to permissible limits. A specific technology is applied for eachpollutant removal. First, selective catalytic reactors (SCR) usuallyprecede other technologies with the aim of accomplishingdenitrification. The options for desulfurization include dry and wetscrubbing. Mercury is effectively controlled with injection of powderedsorbents subsequently removed by particulate control devices.Multi-pollutant control is much desired in an era of increasinglystringent environmental regulations.

Less known and applied, shaped activated carbon pellets have beeninstalled in a fixed bed configuration to provide multipollutant control(to remove sulfur dioxide, sulfur trioxide, mercury, particulate matterand nitrogen oxides from flue gas in a ReACT™ System). Currenttechniques to produce shaped activated carbon pellets for thisapplication involve several production steps and high temperaturetreatments that produce excessive emissions. U.S. Pat. No. 5,840,651describes a method for the production of an activated coke with highactivity for desulfurization and denitrification. The method of suchprior art is comprised of blending coals with different cakingproperties; forming a mixture; oxidizing followed by carbonizing andfollowed by further oxidation. These oxidizing and carbonizing steps areperformed at elevated temperatures to transform the base material withinherently low specific surface area and low activity into a sorbentmaterial suitable for desulfurization and denitrification. Severalformulations include organic binders such as phenolic resins (U.S. Pat.No. 5,736,485) but these also require high temperature (i.e. energyintensive) processing and emit hazardous air pollutants duringproduction.

Other production methods for shaped activated carbon pellets have beendeveloped using clay binders, which circumvent many emission concernsbut still require high temperature processing. Where high strength ofthe shaped sorbent is required, adsorption capacity is typically lost.For example, when clay is used as a binder, increasing the clay fractionfrom 5 to 30% significantly increases hardness. However, adsorption ofbutane, as an example, steadily decreases with the increased fraction ofclay (U.S. Pat. No. 5,488,021).

Lower temperature production methods thus developed from the prior artinsufficiency use cellulosic binder materials (U.S. Patent ApplicationPublication No. 2003/0022787). However, these materials do not exhibitstability in high temperature applications and therefore would not besuitable for use in many process gas applications. There remains a needto produce shaped activated carbon bodies that have improved strengthunder a multitude of operating conditions with high adsorption capacityand reactivity produced at a competitive cost.

SUMMARY OF THE INVENTION

The present invention disclosed herein is directed to a high mechanicalstrength sorbent product, system, and method for controlling multiplepollutants from process gas. In one embodiment, it is a high mechanicalstrength sorbent product capable of simultaneous removal of multiplepollutants from process gas and the process for the production thereof.In general, the process consists of blending one or more base sorbentmaterials with 1 or more binders, water, and additional additives asnecessary; forming said mixture or alternatively coating said mixtureonto a support material; and then drying the formed or coated materialat low temperatures. The sorbent product may be powdered, granular,pelletized or coated onto a support material. Furthermore, the sorbentproduct may be housed in a packed bed through which the process gas maypass, injected into the gas, housed in a rotating system where thesorbent product circulates between contact with the gas and a sorbentregeneration system, or installed in a fixed location in the gas conduitsystem.

The sorbent product combines multiple components in order to (1) addhigh strength without production drawbacks such as high temperaturetreatment or by-product formation, and (2) provide improvedmultipollutant treatment capacity at reduced production costs. The highmechanical strength allows the sorbent product to be used inapplications that require maintaining the original shape and integrityof the product. Such applications might include a moving fixed bed foreither pollution control or regeneration. The sorbent product precursormaterials, which were inventively combined to exhibit these qualities,will also require minimal processing time and energy.

Multipollutant control allows for several contaminants of concern to betreated simultaneously with one pollution control device in lieu ofmultiple single targeted treatment systems. This has significantadvantages including the decreasing of capital cost, technologyfootprint, and waste streams.

In one embodiment, the present invention is directed to a sorbentproduct, including from about 1 wt % to about 99 wt %, based on thetotal weight of the sorbent product, of at least one base sorbentmaterial; and from about 1 wt % to about 99 wt %, based on the totalweight of the sorbent product, of at least one binder. In one aspect,the sorbent product may further include at least from about 0 wt % toabout 99% wt %, based on the total weight of the sorbent product, of atleast one additional additive.

In another aspect, the at least one base sorbent material may be atleast one material selected from the group consisting of activatedcarbon, activated coke, activated charcoal, activated carbon fibers,biochars, chars, zeolites and other molecular sieves, silica sorbents,and polymethylsiloxane polyhydrate. In yet another aspect, the at leastone base sorbent material may have a starting surface area of from about10 to about 1,500 m²/gram. Also, the at least one base sorbent materialmay have an average pore size less than 20 Å and less than 50% of thetotal pore volume is a fraction of mesopores as determined by the BJHmethod.

Additionally, the at least one base sorbent material is from about 15 wt% to about 85 wt %, based on the total weight of the sorbent product.Further, the at least one base sorbent material may be powderedactivated carbon with a starting area of greater than 200 m²/gram. Instill yet another aspect, the at least one base sorbent material may beat least 50 wt % of the total sorbent product. Also, the at least onebinder may be at least one material selected from the group consistingof alumina, aluminates, aluminum, aluminum phosphate, asphalt,attapulgite, bitumen, bentonite clay, borate glass, calcium chromites,calcium compounds, calcium fluoride, calcium germinate, calcium oxide,calcium sulfate, carboxymethlycellulose (CMC), casein, cellulose,cellulose ethers, cement, clay, colloidal silica, epoxy resin, flour,fly ash, fuller's earth, glycerol, guar gum, gums, iron humate, ironoxide, kaolin clay, laponite, lignosulfonates, lime, lime kiln dust,magnesium chloride, magnesium oxide, magnesium sulfate, metal carbides,metal carbonyls, metals, molasses, montmorillonite, natural or syntheticresin, nitrophenols, novalac phenolic resin, organosilicons, phenolresins, phenolic resin polymers, phosphoronitrile dichloride polymers,pickling liquors, pitch, polyacrylonitrile, polyester resins, Portlandcement, potassium silicate, pulp mill wastewater, resin, sawdust,shellac, silica, silicates, silicides, silicon carbide, sodium silicate,starch, tar, wollastonite, and zinc compounds.

In another aspect, the at least one binder may include at least onematerial selected from the group consisting of clays, clay, bentoniteclay, attapulgite, fuller's earth, kaolin clay, laponite, andwollastonite; and at least one material selected from the groupconsisting of colloidal silica, laponite, potassium silicate, silica,silicates, silicides, silicon carbide, and sodium silicate.

In still yet another aspect, the at least one binder may be from about 1wt % to about 50 wt %, based on the total weight of the sorbent product.Additionally, the at least one binder creates a sorbent product that isthermally stable at temperatures up to 450° C. in the presence of watervapor. Also, the at least one additional additive may be at least onematerial selected from the group consisting of ammonia salts (ammoniachloride, ammonia sulfate, etc.), urea, acid, base, nitric acid, ironoxides, complex metal ions (i.e. Fe-EDTA, iron hydroxides, etc.), metal,metal oxide, alkaline earth, metal, sand, etc. In another aspect, the atleast one additional additive may be from about 1 wt % to about 5 wt %,based on the total weight of the sorbent product.

In another embodiment, the present invention is directed to a method formaking sorbent products, including providing a source of at least onebase sorbent material; providing a source of at least one binder;providing a source of water; mixing the at least one base sorbentmaterial, at least one binder, and water to produce a sorbent productmixture; forming the sorbent product mixture into at least one of ashape, form, and coating; and drying the at least one of the shape,form, and coating to produce the sorbent product. In one aspect, themethod may further include providing a source of at least one additionaladditive. In another aspect, the mixing may include mixing the at leastone additional additive. Still yet in another aspect, the mixing mayinclude mixing together the dry compounds then adding and mixing the wetcompounds to the dry compounds.

Also, the forming may include forming the sorbent product mixture intoat least one shape selected from the group consisting of cylindrical,cubic, rectangular, and spherical. Additionally, the forming may includeforming the sorbent product mixture into pellets. In another aspect, thedrying may include drying the formed sorbent product at a temperatureranging from 60° C. to 250° C. Further, the forming may include coatingthe sorbent product mixture onto a substrate. In still yet anotheraspect, the water is from about 15 wt % to about 50 wt %, based on thetotal weight of the sorbent formula.

In yet another embodiment, the present invention is directed to a systemfor controlling multiple pollutants in a process gas, including a sourceof the process gas; and a pollutant control unit containing one or moresorbent products, the one or more sorbent products comprising from about1 wt % to about 99 wt %, based on the total weight of the sorbentproduct, of at least one base sorbent material; and from about 1 wt % toabout 99 wt %, based on the total weight of the sorbent product, of atleast one binder.

In one aspect, the one or more sorbent products may further include atleast from about 0 wt % to about 99% wt %, based on the total weight ofthe sorbent product, of at least one additional additive. Additionally,the pollutant control unit may be one or more units selected from thegroup consisting of a packed bed unit, a direct contact unit, a rotarycontact unit, and a recycling unit. In yet another aspect, the systemmay further include a desorption unit for desorbing the multiplepollutants from the one or more sorbent products.

In still yet another embodiment, the present invention is directed to amethod for controlling multiple pollutants in a process gas, includingcontacting the process gas with one or more sorbent product, the one ormore sorbent product comprising from about 1 wt % to about 99 wt %,based on the total weight of the sorbent product, of at least one basesorbent material; and from about 1 wt % to about 99 wt %, based on thetotal weight of the sorbent product, of at least one binder. In oneaspect, the one or more sorbent products may further include at leastfrom about 0 wt % to about 99% wt %, based on the total weight of thesorbent product, of at least one additional additive. In another aspect,the contacting may include flowing the process gas through a packed bedcomprising the one or more sorbent products. In yet another aspect, thecontacting may include injecting the one or more sorbent products intothe process gas. In still yet another aspect, the method may furtherinclude desorbing the multiple pollutants from the one or more sorbentproduct; and recycling the one or more sorbent product for contactingthe process gas.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the features and advantages of thepresent invention, reference is now made to the detailed description ofthe invention along with the accompanying figures in which correspondingnumerals in the different figures refer to corresponding parts and inwhich:

FIGS. 1A-1D are illustrations of sorbent products according to severalembodiments;

FIG. 2 is a block diagram of a system for making sorbent productsaccording to an embodiment;

FIG. 3 is a flowchart of a process for making sorbent products accordingto an embodiment;

FIG. 4 is a block diagram of a system for controlling multiplepollutants from process gas according to an embodiment;

FIG. 5A is an illustration of a packed bed unit containing sorbentproducts according to an embodiment;

FIG. 5B is an illustration of a direct contact unit containing sorbentproducts according to an embodiment;

FIG. 5C is an illustration of a rotary contact unit containing sorbentproducts according to an embodiment;

FIG. 5D is an illustration of a recycling unit containing sorbentproducts according to an embodiment; and

FIG. 6 is a flowchart of a process for controlling multiple pollutantsfrom process gas according to an embodiment.

DETAILED DESCRIPTION OF THE INVENTION

While the making and using of various embodiments of the presentinvention are discussed in detail below, it should be appreciated thatthe present invention provides many applicable inventive concepts, whichcan be embodied in a wide variety of specific contexts. The specificembodiments discussed herein are merely illustrative of specific ways tomake and use the invention, and do not limit the scope of the presentinvention.

Referring initially to FIGS. 1A-1D, several embodiments of highmechanical strength sorbent products for multiple pollutants controlfrom process gas are schematically illustrated and generally designated100 a-100 d (collectively sorbent products 100). Sorbent products 100may be powdered, granular, pelletized, and/or coated onto a substrate.Further, sorbent products 100 may be any shape, form, and the like. Forexample, sorbent products 100 may be a substantially cylindricalpelletized shape or form, such as sorbent product 100 a.

In another example, sorbent products 100 may be a substantiallyrectangular shape or form, such as sorbent product 100 b. In yet anotherexample, sorbent products 100 may be a substantially spherical shape orform, such as sorbent product 100 c. In still yet another example,sorbent products 100 may be a substantially cubic shape or form, such assorbent product 100 d.

Sorbent products 100 means a sorbent product capable of removing sulfuroxides (SO_(x)), nitrogen oxides (NO_(x)), and/or mercury (Hg) from agas stream, such as flue gas, while meeting the following measurement ofstrength and integrity when produced: Roga Index greater than 95%measured using an apparatus as described in JIS M 8801.

Turning now to FIG. 2, an embodiment of a system for making highmechanical strength sorbent products for multiple pollutants controlfrom process gas is schematically illustrated and generally designated200. System 200 includes a sorbent materials feedstock unit 202 that maybe the source for storing and/or the initial feedstock unit forcontaining and providing a sorbent material to a mixing unit 210 ofsystem 200. Sorbent materials feedstock unit 202 may contain one or moresorbent material feedstocks for providing to mixing unit 210 of system200.

Sorbent materials feedstock unit 202 may contain one or more materialsincluding activated carbon, activated coke, activated charcoal,activated carbon fibers, biochars, chars, zeolites and other molecularsieves, silica sorbents, polymethylsiloxane polyhydrate, etc. with asurface area of preferably 10-1500 square meters per gram (m²/g) andaverage preferable pore size less than twenty Angstroms (20 Å) and lessthan 50% of the total pore volume is a fraction of mesopores asdetermined by the BJH method. In one embodiment, this microporousstructure of the sorbent material feedstock enhances improved contactingand interaction between sorbent material feedstock and binders feedstockthat allows for greater binding strength without sacrificing specificsurface area of sorbent products 100.

System 200 may also include a binders feedstock unit 204 that may be thesource for storing and/or the initial feedstock unit for containing andproviding a binder material to mixing unit 210 of system 200. Bindersfeedstock unit 204 may contain one or more binders feedstocks forproviding to mixing unit 210 of system 200.

Binders feedstock unit 204 may contain one or more materials includingalumina, aluminates, aluminum, aluminum phosphate, asphalt, attapulgite,bitumen, bentonite clay, borate glass, calcium chromites, calciumcompounds, calcium fluoride, calcium germinate, calcium oxide, calciumsulfate, carboxymethlycellulose (CMC), casein, cellulose, celluloseethers, cement, clay, colloidal silica, epoxy resin, flour, fly ash,fuller's earth, glycerol, guar gum, gums, iron humate, iron oxide,kaolin clay, laponite, lignosulfonates, lime, lime kiln dust, magnesiumchloride, magnesium oxide, magnesium sulfate, metal carbides, metalcarbonyls, metals, molasses, montmorillonite, natural or syntheticresin, nitrophenols, novalac phenolic resin, organosilicons, phenolresins, phenolic resin polymers, phosphoronitrile dichloride polymers,pickling liquors, pitch, polyacrylonitrile, polyester resins, Portlandcement, potassium silicate, pulp mill wastewater, resin, sawdust,shellac, silica, silicates, silicides, silicon carbide, sodium silicate,starch, tar, wollastonite, zinc compounds, etc.

Preferably, the selection of the materials of binders feedstock unit 204materials is critical to establish high strength despite low dryingtemperatures that are superior to the prior art. For example, the use ofa silica sol and a clay binder material provide a rigid backbone-likestructure locking in activated carbon particles to create the rigid highmechanical strength. In this aspect, the silica sol undergoespolycondensation to form a strong silica bonded network due to thepresence of multivalent cations present in the clay medium. This networkadds rigidity to the mixture without the need for high temperaturespreviously necessary for use of clay binders.

The combination of the materials of binders feedstock unit 204 alsocontributes to the pore morphology of sorbent products 100 to improvethe multipollutant affinity. In one aspect, the materials of sorbentmaterials feedstock unit 202 may provide the largest fraction of thepore volume, the materials of binders feedstock unit 204 may provideadditional adsorption sites and shape the transport pores to make theactivated carbon adsorption sites accessible.

Also, system 200 may include an additional additives feedstock unit 206that may be the source for storing and/or initial feedstock unit forcontaining and providing an additional additives to mixing unit 210 ofsystem 200. Additional additives feedstock unit 206 may contain one ormore materials that may be added as necessary to improve physical andchemical properties. For example, ammonia salts (ammonia chloride,ammonia sulfate, etc.), urea, acid, base, nitric acid, complex metalions (i.e. Fe-EDTA, iron hydroxides, etc.), metal, metal oxide, alkalineearth metal, etc. may be added to the formula to improve denitrificationand desulfurization. For certain applications that require greaterdensity, iron oxides, sand, etc., may be added.

Additionally, system 200 may also include a water feedstock unit 208that may be the source for storing and/or the initial feedstock unit forcontaining and providing water to mixing unit 210 of system 200.

The materials, compounds, and the like contained in sorbent materialsfeedstock unit 202, binders feedstock unit 204, additional additivesfeedstock unit 206, and/or water feedstock unit 208 may be fed into amixing unit 210, in one embodiment. In one aspect, the materials,compounds, and the like in each one of the feedstock units may be feddirectly into mixing unit 210. In another embodiment, they may first befed into a manifold and the like and then fed together into mixing unit210 as is commonly known to those skilled in the art. Mixing unit 210mixes feedstocks 202, 204, 206, and/or 208 into a mixture for furtherprocessing in system 200.

Mixing unit 210 may provide for the mixing of the materials, compounds,and the like that are fed to it from feedstocks 202, 204, 206, and/or208. In one embodiment, mixing unit 210 may be capable of mixing thesematerials, compounds, and the like from feedstocks 202, 204, 206, and/or208 for any desirable amount of time.

In one embodiment, all of the dry feedstocks may be mixed first, andthen the wet binders, water, etc. may be added to the dry mix to createa sorbent mixture.

System 200 may further include a forming unit 212 for receiving themixed material from mixing unit 210 and for then forming the mixedmaterial into a desired shape or form prior to drying as discussedbelow. Preferably, forming unit 212 forms or shapes the mixed materialinto cylindrical, spherical, square, or rectangular granules/pelletsusing an extruder, briquetting machine or pelletizer, as shown in FIGS.1A-1D. In another embodiment, forming unit 212 may be a coating unit forcoating a desired substrate with the mixed material from mixing unit210. In one embodiment, forming unit 212 may be capable of forming saidmixture material into cylindrical pellets through extrusion through adie and cutting the extruding material to produce pellets. In oneembodiment, the extrusion device may be any size die, capable ofproducing the desirable sized pellets. For example, the die may be a 1-3inch die having a desired number of holes for producing the desiredpellets. In one example, the die may be a 2 inch having 6 holes forproducing the desired pellets. Preferably, the pellets have a diameterof from about 2 mm to about 10 mm. More preferably, the pellets may havea diameter of from about 5 mm to about 10 mm. In one preferredembodiment, the pellets may have a diameter of approximately 9 mm.

System 200 may further include a drying unit 214 for drying the shaped,formed, coated, etc. material in a controlled temperature environmentfor a desired amount of time. For example, in one embodiment, dryingconditions inside drying unit 214 may occur at temperatures of 60-250°C. with 110° C. as ideal. Furthermore, in one embodiment, dryingconditions in drying unit 214 may occur using a waste heat source tofurther improve the economics and sustainable production of sorbentproducts 100. Some exemplary drying units 214 may include, but are notexclusive, to rotary kilns, vertical furnaces, any form of waste heat,UV, steam, etc. In one embodiment, drying unit 214 may be capable ofdrying the formed mixture material at a temperature of 110 C to amoisture content of less than 3%.

Referring now to FIG. 3, an embodiment of a method for making highmechanical strength sorbent products for multiple pollutants controlfrom process gas is schematically illustrated and generally designated300. In step 302, the raw materials from one or more feedstocks 202,204, 206, and/or 208 are supplied, fed, provided, etc. to mixing unit210. This step may include weighing, measuring, monitoring, etc. each ofthe one or more feedstocks 202, 204, 206, and/or 208 prior to or duringfeeding into mixing unit 210.

In step 304, the mixture material is mixed to a desired consistency fora desired period of time. In step 306, the mixed material may be fed,supplied, provided, etc. to forming unit 212 for forming into a desiredshape, form, and/or coating. This step may include providing a desirablesubstrate upon which a coating may be applied. In step drying unit 308,the formed or coated material is then supplied, provided, etc. to dryingunit 214 for drying. Although the above method is described withrelation to system 200, the method may be performed in any unitaryand/or modular units and devices as are commonly known to those skilledin the art.

Some exemplary formulations and process conditions for producing sorbentproducts 100 are provided as follows. In one embodiment, a combinationof one or more base sorbent materials, such as supplied from sorbentmaterials feedstock unit 202, may be incorporated with each base sorbentmaterial comprising 1-99 wt. % of the formula for preparing sorbentproducts 100. Ideally, the base sorbent material(s) will comprise nomore than 85 wt. % of the formula and no less than 15 wt. % of theformula. In an ideal embodiment, the base sorbent material is powderedactivated carbon with starting surface area greater than 200 m²/g and isat least 50 wt. % of the total weight of the sorbent products 100.

Also, any binder material suitable for the application, such as suppliedfrom binders feedstock unit 204, may be used singularly or incombination with other binding materials with each binder usedcomprising 1-99 wt. % of the formula for a high mechanical strengthsorbent product. Ideally, a given binder will comprise no more than 50wt. % of the formula and no less than 1 wt. % of the formula. In oneembodiment, no more than two binders are used, with each comprisingabout 1-25 wt. % of the formula. In another embodiment, the preferredbinders create a sorbent product that is thermally stable attemperatures up to 450° C. in the presence of water vapor, thusmaintaining the high mechanical strength of the sorbent product.

Further, additional additives, such as supplied from additionaladditives feedstock unit 206, each may comprise 0-99 wt. % of theformula. Ideally, additional additives will each comprise 5 wt. % of thetotal weight of the sorbent product. Additionally, in one embodiment,water may be added at 15-50 wt. % during the mixing of raw materials,such as when mixing in mixing unit 210.

The present sorbent products 100 are capable of simultaneousdesulfurization (deSO_(x)), denitrification (deNO_(x)), and/or mercury(Hg) removal, and some generalized and specific examples are describedbelow. It is noted however, that these examples represent improvedresults and the technical scope of the invention herein is not limitedto the examples. In the following examples, the properties andperformance of the sorbent product was measured by the followingmethods.

SO₂ adsorption capacity. The sorbent product was size reduced to lessthan 1.7 mm particles and approximately 2 grams placed in a quartz fixedbed reactor where it was exposed to the following simulated flue gasconditions: SO₂ at 20,000 ppm, O₂ at 5%, H₂O at 10% and N₂ as thebalance. The flue gas was set to a temperature of 100° C. and passedthrough the sorbent product for 3 hours. Finally, a desorption step at atemperature of 400° C. was performed under an N₂ environment and thedesorbed SO₂ was measured with a Fourier Transfer Infrared (FTIR)device.

deNO_(x) efficiency. To determine the deNO_(x) efficiency: 130 g of thesorbent product was placed in a quartz tube reactor where it was exposedto the following simulated flue gas conditions: NO at 200 ppm, O₂ at 5%,H₂O at 10%, NH₃ at 200 ppm and N₂ as the balance. The flue gas was setto a temperature of 130° C. and space velocity of 400 hr⁻¹. The NOconcentration as measured by FTIR at the outlet after 50 hours was usedto determine the percent deNO_(x) efficiency.

Roga Index. To determine the Roga Index: 30 grams of the sorbent productwith size greater than 6 mm was placed in an apparatus as described inJIS M 8801. The apparatus was set to rotate at 50 rpm for 1,000revolutions after which the sample was sieved through a 6 mm mesh for 3minutes. The Roga Index is the weight retained in the sieve divided bythe weight of the sample.

In one embodiment, a generalized process and formulation for makingsorbent products 100 may include: blending 1 or more base sorbentmaterials each constituting 1-99 wt. % of the formula with 1 or morebinders each constituting 1-99 wt. % of the formula, additionaladditives as necessary to improve physical and chemical properties eachconstituting 0-99 wt. % and adding water constituting 0-99 wt. % of theformula. Mixing the blended raw materials to an even consistency for1-30 minutes. Forming said mixture into cylindrical, spherical, square,or rectangular granules/pellets using an extruder, briquetting machineor pelletizer. Drying pellets at temperatures ranging from 60°-250° C.to a moisture content of 0-15% per ASTM method D2867.

In another embodiment, a generalized process and formulation for makingsorbent products 100 may include: blending 1 or more base sorbentmaterials each constituting 1-99 wt. % of the formula with 1 or morebinders each constituting 1-99 wt. % of the formula, additionaladditives as necessary to improve physical and chemical properties eachconstituting 0-99 wt. %, and adding water constituting 0-99 wt. % of theformula. Mixing the blended raw materials to an even consistency for1-30 minutes. Coating said mixture onto a support material. Dryingcoated material at temperatures ranging from 60°-250° C. for durationsufficient enough to reach steady mass.

Some more specific exemplary formulations and processes for makingsorbent products 100 are described below.

Example 1

A high mechanical strength sorbent product was made as follows: blendinga powdered activated carbon with initial surface area of 750 m²/g,average pore size of 22 Å, and 27% mesopore fraction as 42 wt. % of theformula with 11 wt. % bentonite and 4 wt. % iron oxide. Adding a 40 wt.% solution of colloidal silica as 19 wt. % of the formula and waterconstituting 24 wt. % of the formula, and then mixing for 5 minutes.Forming said mixture into 9 mm diameter cylindrical pellets throughextrusion with a 6 hole, 2 inch dye and cutting the extruding materialto produce pellets with 10 mm approximate length. Drying extrudedpellets at a temperature of 110° C. to a moisture content of less than3%. The resulting sorbent product 100 (Experiment 1 in Table 1) had aRoga index of 95%, SO₂ adsorption capacity of 90 mg/g, and deNO_(x)efficiency of 17%.

Example 2

A high mechanical strength sorbent product was made as follows: blendinga powdered activated carbon with initial surface area of 220 m²/g,average pore size of 32 Å, and 55% mesopore fraction as 42 wt. % of theformula with 14 wt. % lime kiln dust. Adding a 40 wt. % solution ofcolloidal silica as 18 wt. % of the formula and water constituting 26wt. % of the formula, and then mixing for 5 minutes. Forming saidmixture into 9 mm diameter cylindrical pellets through extrusion with a6 hole, 2 inch dye and cutting the extruding material to produce pelletswith 10 mm approximate length. Drying extruded pellets at a temperatureof 110° C. to a moisture content of less than 3%. The resulting sorbentproduct 100 (Experiment 2 in Table 1) had a Roga index of 93%, SO₂adsorption capacity of 14 mg/g, and deNO_(x) efficiency of 7%. Thissorbent product exhibits lower SO₂ adsorption capacity and deNO_(x)efficiency than the sorbent product in Example 1 due to the use of abase sorbent material with a large average pore size, which does notproduce sufficient active sites for SO_(x) adsorption anddenitrification.

Example 3

A sorbent product with low mechanical strength was made as follows:blending a powdered activated carbon with initial surface area of 570m²/g, average pore size of 20 Å, and 20% mesopore fraction as 50 wt. %of the formula with 10 wt. % bentonite. Adding water constituting 40 wt.% of the formula, and then mixing for 5 minutes. Forming said mixtureinto 9 mm diameter cylindrical pellets through extrusion with a 6 hole,2 inch dye and cutting the extruding material to produce pellets with 10mm approximate length. Drying extruded pellets at a temperature of 110°C. to a moisture content of less than 3%. The resulting sorbent product100 (Experiment 3 in Table 1) had a Roga index of 85%, thus producinginsufficient mechanical strength due to lack of high temperaturetreatment as described in the prior art for shaped activated carbonpellets with clay binders.

Example 4

A sorbent product with low mechanical strength was made as follows:blending a powdered activated carbon with initial surface area of 220m²/g, average pore size of 32 Å, and 55% mesopore fraction as 50 wt. %of the formula with 10 wt. % bentonite. Adding water constituting 40 wt.% of the formula, and then mixing for 5 minutes. Forming said mixtureinto 9 mm diameter cylindrical pellets through extrusion with a 6 hole,2 inch dye and cutting the extruding material to produce pellets with 10mm approximate length. Drying extruded pellets at a temperature of 110°C. to a moisture content of less than 3%. The resulting sorbent product100 (Experiment 4 in Table 1) had a Roga index of 65%, thus producinginsufficient mechanical strength due to lack of high temperaturetreatment as described in the prior art for shaped activated carbonpellets with clay binders. Furthermore, the lack of sufficientmicropores (pores less than 20 Å) contributed to a decrease inmechanical strength in comparison to Example 3.

Example 5

A sorbent product with low mechanical strength was made as follows:blending a powdered activated carbon with initial surface area of 220m²/g, average pore size of 32 Å, and 55% mesopore fraction as 54 wt. %of the formula with 3 wt. % bentonite and 3 wt. % starch. Adding waterconstituting 40 wt. % of the formula, and then mixing for 5 minutes.Forming said mixture into 9 mm diameter cylindrical pellets throughextrusion with a 6 hole, 2 inch dye and cutting the extruding materialto produce pellets with 10 mm approximate length. Drying extrudedpellets at a temperature of 110° C. to a moisture content of 3%. Theresulting product (Experiment 5 in Table 1) had a Roga index of 85%,thus producing insufficient mechanical strength due to lack of hightemperature treatment as described in the prior art for shaped activatedcarbon pellets with clay binders.

TABLE 1 Summary of Experimental Results Base Base Base Sorbent SorbentSorbent BJH SO₂ Surface Average Mesorpore Roga adsorption deNO_(x)Experi- Area Pore Fraction Index capacity efficiency ment (m²/g) Size(Å) (%) (%) (mg/g) (%) 1 750 22 27 95 90 17 2 220 32 55 93 14  7 3 57020 20 85 47 NA 4 220 32 55 65 NA NA 5 220 32 55 85 NA NA

Turning now to FIG. 4, an embodiment of a system for controllingmultiple pollutants from process gas according to an embodiment isschematically illustrated and generally designated 400. System 400 mayinclude a source of process gas, waste gas, etc. such as a boiler 402for a coal-fired power plant. Although the example described hereinapplies to coal-fired power plants, the process gas or flue gas to betreated may originate from many industrial facilities such as a powerplant, cement plant, waste incinerator, or other facilities that willoccur to one skilled in the art. Such gas streams contain manycontaminants that are desirable to decrease in concentration forprotection of health and the environment. Nevertheless, the presentmethod is being described for removing sulfur dioxide, sulfur trioxide,mercury, particulate matter and nitrogen oxides from a coal-fired powerplant gas stream using the shaped activated carbon pellet. Boiler 402may be a coal-fired boiler that burns coal to heat water intosuperheated steam for driving steam turbines that produce electricity.These types of power plants are common throughout the U.S. andelsewhere.

The process gas or flue gas may then be ducted and piped to a heatexchanger or pre-heater 404 where heat is transferred from the flue gasto a feed of air to be fed back into boiler 402. The flue gas may thenbe transferred to a pollutant control unit 406 for deSO_(x) control,deNO_(x) control, and/or Hg removal. After being treated in pollutantcontrol unit 406, the treated flue gas may then be sent to a stack 408for emission into the environment.

With reference to FIG. 5, pollutant control unit 406 may include manydifferent embodiments that contain sorbent products 100 for controllingdeSO_(x) and deNO_(x) and/or removing Hg simultaneously in one unit. Forexample, pollutant control unit 406 may be a packed bed 502 a that ispacked with sorbent products 100 for passing flue gas through for thesimultaneous control of deSO_(x) and deNO_(x), and/or removal of Hg.After treatment, the flue gas may then be transferred to stack 408 foremission to the environment.

In another embodiment, pollutant control unit 406 may be a directcontact unit 502 b where a supply of sorbent products 100 is injectedvia a line with nozzles 504 into a vessel 506 where it directlycontacts, possibly in a counterflow stream, the stream of flue gas forcontrolling deSO_(x) and deNO_(x) and/or Hg removal. After treatment,the flue gas may then be transferred to stack 408 for emission into theenvironment.

In yet another embodiment, pollutant control unit 406 may be a rotarycontact unit 502 c where flue gas is contacted with sorbent products 100for controlling deSO_(x) and deNO_(x) and/or Hg removal. Aftertreatment, the flue gas may be transferred to stack 408 for emission tothe environment. In still yet another embodiment, pollutant control unit406 may be a recycled contact unit 502 d having a slow moving bed and/orcarousel where the contacted sorbent products 100 is sent to adesorption unit and/or recycle unit 508 where it may be desorbed of thesorbed pollutants prior to being sent back into recycled contact unit502 d.

In this embodiment, recycled contact unit 502 d may be any type ofvessel or unit that contains a plurality of mobile media 507 that iscapable of a fluid type flow (as shown by arrow) within the vessel orunit as is known to those skilled in the art. Mobile media 507 may betreated, coated, and/or have disposed about it or within it the coatingor sorbent products 100 as described herein. A process or flue gas isfed through recycled contact unit 502 d for contacting with the fluidflowing mobile media 507 having sorbent products 100 and/or coatingwhere the pollutants and/or contaminants contained in the process orflue gas are adsorbed by the mobile media 507. Mobile media 507 may thenbe transferred to recycle unit 508 where by application of heat or othertechnology the pollutants and/or contaminants are desorbed from mobilemedia 507. Mobile media 507 may also have a fluid type flow withinrecycle unit 508 (as shown by arrow) for improved operation and contactwith operating conditions therein. After treatment, the flue gas may betransferred to stack 408 for emission to the environment. Also, thedesorbed mobile media 507 may then be recycled back into recycledcontact unit 502 d for reuse.

Turning now to FIG. 6, a method for simultaneously controlling deSO_(x)and deNO_(x) and/or Hg removal in flue gas or process gas isschematically illustrated and generally designated 600. In step 602,process or flue gas may be transferred to a pre-heater for heat transferto an air source to be fed back into a particular unit, such as boiler402. In step 604, the process or flue gas is transferred to pollutantcontrol unit 406 for simultaneous control of deSO_(x) and deNO_(x)and/or Hg removal. This step may include contacting the process or fluegas with sorbent products 100 for controlling deSO_(x) and deNO_(x)and/or Hg removal. This step may also include recycling and desorbingnitrogen and sulfur compounds from sorbent products 100. This step mayfurther include flowing or transferring the contacted sorbent products100 to a desorption unit for desorbing the multiple pollutants from thesorbent products 100. In step 606, the treated process or flue gas maybe transferred to stack 408 for emission into the environment.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments as well as other embodiments of the inventionwill be apparent to persons skilled in the art upon reference to thedescription. It is, therefore, intended that the appended claimsencompass any such modifications or embodiments.

What is claimed is:
 1. A sorbent product for removing sulfur oxides,nitrogen oxides, and/or mercury (Hg) from a gas stream, comprising: fromabout 1 wt % to about 99 wt %, based on the total weight of the sorbentproduct, of at least one base sorbent material; from about 1 wt % toabout 99 wt %, based on the total weight of the sorbent product, of atleast one binder; from about 1 wt % to about 5 wt %, based on the totalweight of the sorbent product, of at least one additional additiveselected from ammonia salts and metal; and wherein said at least onebinder forms a bonded network for supporting said at least one basesorbent material, and wherein said sorbent product does not containsulfur.
 2. The sorbent product as recited in claim 1, wherein the atleast one base sorbent material is at least one material selected fromthe group consisting of activated carbon, activated coke, activatedcharcoal, activated carbon fibers, biochars, chars, zeolites and othermolecular sieves, silica sorbents, and polymethylsiloxane polyhydrate.3. The sorbent product as recited in claim 1, wherein the at least onebase sorbent material has a starting surface area of from about 10 toabout 1,500 m.sup.2/gram.
 4. The sorbent product as recited in claim 1,wherein the at least one base sorbent material has an average pore sizeless than 20.ANG. and less than 50% of the total pore volume is afraction of mesopores as determined by the BJH method.
 5. The sorbentproduct as recited in claim 1, wherein the at least one base sorbentmaterial is from about 15 wt % to about 85 wt %, based on the totalweight of the sorbent product.
 6. The sorbent product as recited inclaim 1, wherein the at least one base sorbent material is powderedactivated carbon with a starting area of greater than 200 m.sup.2/gram.7. The sorbent product as recited in claim 1, wherein the at least onebase sorbent material is at least 50 wt % of the total sorbent product.8. The sorbent product as recited in claim 1, wherein the at least onebinder is at least one material selected from the group consisting ofalumina, aluminates, aluminum, aluminum phosphate, asphalt, attapulgite,bitumen, bentonite clay, borate glass, calcium chromites, calciumcompounds, calcium fluoride, calcium germinate, calcium oxide, calciumsulfate, carboxymethlycellulose (CMC), casein, cellulose, celluloseethers, cement, clay, colloidal silica, epoxy resin, flour, fly ash,fuller's earth, glycerol, guar gum, gums, iron humate, iron oxide,kaolin clay, laponite, lignosulfonates, lime, lime kiln dust, magnesiumchloride, magnesium oxide, magnesium sulfate, metal carbides, metalcarbonyls, metals, molasses, montmorillonite, natural or syntheticresin, nitrophenols, novalac phenolic resin, organosilicons, phenolresins, phenolic resin polymers, phosphoronitrile dichloride polymers,pickling liquors, pitch, polyacrylonitrile, polyester resins, Portlandcement, potassium silicate, pulp mill wastewater, resin, sawdust,shellac, silica, silicates, silicides, silicon carbide, sodium silicate,starch, tar, wollastonite, and zinc compounds.
 9. The sorbent product asrecited in claim 1, wherein the at least one binder comprises: at leastone material selected from the group consisting of clays, clay,bentonite clay, attapulgite, fuller's earth, kaolin clay, laponite, andwollastonite; and at least one material selected from the groupconsisting of colloidal silica, potassium silicate, silica, silicates,silicides, silicon carbide, and sodium silicate.
 10. The sorbent productas recited in claim 1, wherein the at least one binder is from about 1wt % to about 50 wt %, based on the total weight of the sorbent product.11. The sorbent product as recited in claim 1, wherein the sorbentproduct is thermally stable at temperatures up to 450.degree. C. in thepresence of water vapor.
 12. The sorbent product as recited in claim 1,wherein the at least one additional additive additionally comprises atleast one material selected from the group consisting of ammoniachloride, ammonia sulfate, urea, acid, base, nitric acid, iron oxides,complex metal ions, Fe-EDTA, iron hydroxides, metal oxide, alkalineearth metal, and sand.
 13. A system for removing sulfur oxides, nitrogenoxides, and/or mercury (Hg) in a process gas, comprising: a source ofthe process gas; a pollutant control unit containing one or more sorbentproducts, the one or more sorbent products comprising from about 1 wt %to about 99 wt %, based on the total weight of the sorbent product, ofat least one base sorbent material; and from about 1 wt % to about 99 wt%, based on the total weight of the sorbent product, of at least onebinder; and from about 1 wt % to about 5 wt %, based on the total weightof the sorbent product, of at least one additional additive selectedfrom ammonia salts and metal; and wherein said at least one binder formsa bonded network for supporting said at least one base sorbent material,and wherein said one or more sorbent products does not contain sulfur.14. The system as recited in claim 13, wherein the pollutant controlunit comprises: one or more units selected from the group consisting ofa packed bed unit, a direct contact unit, a rotary contact unit, and arecycling unit.
 15. The system as recited in claim 13, furthercomprising: a desorption unit for desorbing the multiple pollutants fromthe one or more sorbent products.